Although portable swivel seats with uni- or tripod collapsible legs are known as shown in the following prior U.S. Pat. Nos.:
Powell: 216,629; issued June 17, 1879; Class 248/425; PA1 Birdsall: 582,338; issued May 11, 1897; Class 297/17(X); PA1 Mowrey: 1,325,164; issued Dec. 16, 1919; Class 108/157(X); PA1 Boerma: 3,283,733; issued Nov. 8, 1966; Class 108/159; PA1 Harris: 3,589,661; issued June 29, 1971; Class 297/193(X).
No reference was found with the specific two different-size bearing sockets in a seat nor a hollow seat with a removable lid to provide a storage container for articles.